Composition for hardening steel



Patented June 24, 1924.

UNITED STATES PATENT oF icE.

WILLIAM CLYDE sassnrnor Lone BEACH, CALIFORNIA.

COMPOSITION FOR N Drawing. Application filed November To all whom it may concern.

Be it known that I, WILLIAM CLYDE BAS: snr'r, a citizen of United States, residing at Long Beach, in the county of Los Angeles and State of California, have invented new and useful Improvements in Composition for Hardening Steel, of which the following is a specification.

The present invention relates to hardening and tempering steel, by a case-hardening and carbonizing method.

The invention comprises heating the steel articles, in boxes or pipe, while packed in a particular mixture described in detail below, the temperature being carried, as is usual, up to about 1600 or 1700 F.

The composition in its preferred form consists of 24 parts of fine sawdust, preferably sawdust from hard wood, to which is added 1 part of carbonate of soda in powder form, the monohydratedcarbonate of soda being preferably used, 1 part of magnesium carbonate in the form of a fine powder, and 10 parts of fine charcoal. Some grades of sodium carbonate also contain a small amount of sodium. chloride, and for very fine work,

I preferably would not use such impure soda,

but would prefer a purified soda, free from chloride. After mixing the four materials thoroughly, the mixture is then used in the ordinary manner as above described. With my composition, it is immaterial if the pieces of steel in the box should actually touch each other at places. With many of the compounds previously used, the pieces of steel in the box must be completely separated from each other by a layer of the casehardening composition. A further advantags of my composition is, that the hardening is completed in a shorter time, and the saving of time may amount to about one third or one fourth of the total amount of time used. The steel product, when treated, gives a very hard surface, which surface will vary in thickness according to the time treated, usually leaving a soft core with the hardened casing or surface around it. Such a product will stand hard use, hammering and strain without breaking{ The surface may in some cases break if hammered excessively, but the cracked or broken surface portion Will rigidly adhere to the soft core. A further advantage which is of great importance is that the use of this com- HARDENING STEEL. 1

18, 1922. Serial No. 601,900.

position removes the major part or all of the sulphur present in the steel, so that the steel is in fact considerably purified by the use of this composition.

If it is desired to do so, the treatment can be continued for a sufficiently long time to harden the article clear through. This is particularly important in the treatment of thin articles such as knives and the like. The steel can be hardened to a sufficient degree to readily cut glass, by the use of the composition above described.

It will be obvious that the steel treated in accordance with this process possesses superior wearing qualities.

The compound can be reused many times without injuring the steel in any manner. The steel treated can be readily forged or drawn out by the ordinary methods of forging and drawing, the hardened coating or exterior being in this case reduced in thickness but not in quality.

It will be understood that after the steel in the box has been heated to the desired temperature, say 1600 F., or so, the box is removed and is allowed to cool, after which the contents of the box are removed. The steel maythen be again heated up to 1600 F or so, and again allowed to cool, and then the steel can be tempered in the ordinary manner. Steel which has been heated in the composition can be polished. For example, if a bright piece of finished steel is hardened by this method, the surface will then be found to have the same appearance as the original, except that the surface will be of a dark color caused by the heat. The article can again be polished without the production of any rough spots in the surface.

It appears probable that the hardening operation dependsupon the formation of vapor which penetrates the heated steel article, the heat serving to open the pores of the article to some extent, whereby the vapors can be absorbed by the steel. The thickness of the surface coatingor case can be regulated by regulating the time that the article is held at the high temperature, imbedded in the composition. Experiments have indicated that the case or coating will run from 1.1% to 1.2% carbon.

In the above formula I have given the preferred proportions of the ingredients but it is to be understood that these proportions can be varied to some extent, dependdients together constituting somewhat over 5% of the entire mixture.

2. A compound for case-hardening steel, comprising about 24 parts of fine hard wood sawdust, about 10 parts of powdered charcoal, about 1 part of sodium carbonate, and about 1 part of magnesium carbonate.

In testimony whereof I affix my signature.

WILLIAM CLYDE BASSETT. 

